Refrigeration



F. M. RAVER REFRIGERATION Jan. 19, 194.

5 Sheets-Sheet 1 Filed Dec. 7, 1939 W Mm A INVENTOR I'rancis M. Ea 1/61 BY Jan 19, 1943. M RAVER 2,398,543

REFRIGERATION Filed, Dec. 7, 1939 3 Sheets-Sheet 2 Jim; 1943- F. M. RAVER 2,368,541

REFRIGERATION Filedbec. 7, 1939 s Sheets-Sheet s INVENTOR Franczs M. Bauer ail 2.1 allure M19 KTTORNEY Patented Jan. 19,194:

Francis M. Raver, York, Pa minor, by memo FlakiceCorporation, Broo assignments, to

N. Y., a corporation of Delaware Application December 7, 1939, Serial No. 307,978

This invention relates to the forming of solid products from fluid, and in certain particulars to a method and apparatus for making ice. The embodiment of the invention hereinafter set forth is especially adapted to the manufacture of fragments of congealed or frozen liquids containing water as a predominant constituent.

An object of this invention is to provide apparatus for and a method of converting liquids into solids on a rigid freezing surface and for removing the solids therefrom, all in an efficient and dependable manner. Another object is to provide a new and improved refrigeration system. A further object is to provide apparatus which is sturdy in construction and economical to build and operate and which embodies various of the above features. These and other objects will be in part obvious and in part pointed out below.

The invention accordingly consists in the features of construction, combinations of elements, arrangements of parts and in the several steps and relation and order of each of the same to one or more of the others, all as will be illustratively described herein, and the scope of the application of which will be indicated in the following claims.

In the drawings:

Figure l is a vertical section on line l-i of Figure 2, showing apparatus embodying the invention for forming ice on a rotating cylinder and for removing the ice from the cylinder;

Figure 2 is an axial vertical section on the line 22 of Figure 1;

Figure 3 is a schematic view-showing the refrigerant circuit of the apparatus; and

Figure 4 is an enlarged perspective view of the ice-removing wedge unit in operation.

The present embodiment of the invention deals primarily with the congealing of a liquid, such I as water, on a substantially rigid surface and the removal of the congealed liquid from the surface in the form of flakes in contradistinction to the finely comminuted ice or snow which may be scraped fromv a sheet of ice remaining on a rigid surface on which it is frozen. The problem of removing ice or other aqueous fluids congealed on a rigid freezing. surface is diflicult because of the tenacity with which the congealed material clings to the freezing surface, and also because of the peculiar characteristics of the congealed substances, such, for example, as the hardness, brittleness and tensile and compressive strengths.

It has long been recognized that scraping ice from a freezing surface has many disadvantages such as consuming considerable power and producing a substance which, because of its fineness and other qualities, is limited in its use as a refrigerant. In the present invention, the ice is frozen on a smooth, substantially rigid metal cylindrical surface and is removed therefrom by a radially pushing and wedging action rather than by a. tangential cutting or scraping action. Furthermore, the temperature of the ice at the point of removal is controlled, 1. e. is tempered, to regulate the hardness and brittleness of the ice to maintain these characteristics at such values that the wedging and pushing action frees successive strips of the sheet of ice completely from the freezing surface. The conditions are further controlled in such a manner that when, for example, water-ice is being frozen, the ice is peeled off at a predetermined thickness which may be less than an eighth of an inch.

Referring particularly to Figure 1 of the draw ings, refrigerant such, for example, as dichlorodifluoromethane is delivered in liquid form to a cylinder generally indicated at l, which serves as a flooded evaporator having a cylindrical cooling surface. Within this cylinder, the refrigerant is evaporated thereby to produce refrigeration, and the gaseous refrigerant is withdrawn. This cylinder 4 is rotatably mounted in a tank 2 of water and is slowly rotated counterclockwise so that a sheet of ice forms on the cylindrical cooling surface and the ice is then removed at the top of the cylinder where the cylinder extends above the water. The ends of the cylinder are insulated so that ice forms only on the cylindrical surface.

The ice is removed from the cylindrical surface by a cutting-wedging unit indicated at 8, which in appearance resembles a lawn mower cutter, but which, instead of having cutter blades, is provided with a, plurality of wedges, preferably helical, with sharp edges along the trailing sides of the wedges, and mounted to rotate'freely about an axis directly above the cylinder. The axis of the wedge unit is parallel to the axis of the cylinder and is spaced therefrom such a distance that the outer sharp edges of the wedges move during rotation almost to contact the coolin surface of the cylinder. Thus, the path through which the wedges move is substantially tangential to the evaporator cooling surface, and the wedges engage and move with the sheet of ice on the cooling surface thereby to rotate the wedge unit. By providing helical wedges mounted in the manner herein described, there is a ice at the time the ice is wedged free from the 7 cylinder. and at the same time. the feed water is precooled. The water in tank 2 is further precooled. as shown at the right of the figure. by a heat-exchange pipe I0, through which the refrigerant passes as it leaves the evaporator. all as will be pointed out below.

As shown best in Figure 2. cylinder 4 is formed by a cylindrical steel shell 28 welded to a pair of end walls 30 and 32. At the left, end wall 30 is welded to a stub shaft l2 which is supported by a cap hearing I 4 clamped in place by stud bolts l5 which are received by a flange l1 welded to the side wall l6 of tank 2. At the right, end wall 32 is rigidly secured by means of a plurality of stud bolts 34 to a flange 35 welded to a sleeve shaft l8. Sleeve shaft I8 is provided with a sleeve bearing 24 which is received in a bearing 20 clamped in place by stud bolts 2| which are threaded into a flange 23 welded to the side wall 22 of tank 2.

Liquid refrigerant is supplied to cylinder 4 through pipe 45 extending through the center of sleeve shaft l8; after the liquid refrigerant evaporates, it is withdrawn through a pipe 48 surrounding and concentric with pipe 46. Pipe 46 extends downwardly and delivers the liquid refrigerant to the bottom of the cylinder, while pipe 48 extends upwardly and receives the gas refrigerant through its open end near the top of the cylinder. Power to rotate the cylinder is transmitted to the right end of sleeve shaft l8 through a gear 50 which is keyed to the shaft. The outside of sleeve shaft I8 is sealed by a pack-' ing gland, indicated at 26, mounted on the righthand end of. bearing 20, and the inside of the sleeve shaft is sealed by a packing gland 52 at v the right of gear 50.

In the present embodiment, the cylinder shell 28 is formed of stainless steel having eighteen per cent chromium and eight per cent nickel, with the outer surface ground and polished to a standard No. 4 finish. As has been indicated above. ice is formed only upon this cylindrical surface. and accordingly, end walls 30 and 32 are covered by rubber insulating rings 36 and 38, respectively, which are held in place by cover plates 40 and 42, respectively. Cover plates 40 and are secured to their respective end walls bya plurality of tapped lugs 44.

The wedge unit 6 comprises six helical wedges 54 (see also Figure 4) which are carried by means of five spaced supporting rings 56 upon a shaft 58, each wedge extending the length of the cylinder and extending in an arc of 80 around their own axis. The six wedges thus overlap with the leading end of each wedge overlapping the trailing end of the next wedge to an extent of approximately 20". Wedges 54 are beveled so that the sharp edge of each wedge becomes th leading edge as the 'wedge rotates as shown in Figure 1. Shaft 58 is supported at its ends by a pair of bearing units 60 which are mounted upon the upper edges of the side walls of tank 2; bearing units 60 are of the anti-thrust ball-bearing type with suitable oil retaining means. So mounted, wedge unit 6 is free to rotate. and when cylinder 4 rotates (see Figural), the sheet of ice upon the cylinder 4 is subjected progressively to the spray 8 and engages the wedge unit; in effect. the wedge unit rolls on the freezing surface and is thereby rotated with a peripheral speed the same as that of the freezing surface.

Due to the arcuate overlapping of the helical wedges, there is always a wedge in contact with the sheet of ice: and as the trailing end of one wedgexetreats from the ice, the leading end of the next wedge moves against the ice (Figure 4) During the movement of each wedge toward cylinder 4. the leading end of the sharp edge of the wedge first engages'the surface of the ice. Upon continuedrotation of the cylinder, this leading end of the wedge is forced down into the ice and then withdrawn from the ice; this action is progressive alongthe entire length of the wedge from its leading end to its trailing end. Referring to Figure 1. during this movement, the ice on the cylinder at the left of the wedge is wedged toward the left. thus sliding tangentially with respect to the surface on which it was formed. In this manner, the ice is stripped free from the cylinder and passes to the left (Figure 1) over a collector blade 62 and down a chute 54. Each succeeding wedge 54 frees the ice upon the cylinder between the line where it makes contact with the ice on the cylinder and the line where the next preceding blade had made such contact (see Figure 4). Due to the helical shape of the wedges. each wedge removes a strip of ice from the cylinder which extends at an angle to the axis of the cylinder, and the wedging action is to a certain extent normal to the wedges. Extending over the top of wedge unit I is a cover I which is attached at its ends to the supports for hearing units 60.

The refrigerant circuit for this embodiment of the apparatus is shown diatically in Figure 3. Liquid refrigerant is supplied at the lower left-hand side of the figure through a pipe 66 and passes successively through a strainer 68 and a control valve I4. From control valve 14. the liquid refrigerant passes through pipe 46 to the bottom of cylinder 4, where, as outlined above. the refrigerant evaporates and leaves the cylinder through pipe 48.-

Under normal operating conditions, lubricating oil accompanies the liquid refrigerant entering the cylinder and it is important that this oil I be returned to the compressor-condenser unit.

In the'present embodiment, this oil is removed from the evaporator through pipe 48 with the v gaseous refrigerant and a small quantity of liquid refrigerant. This is accomplished by supplying an excess quantity of liquid refrigerant to the evaporator so that there is a. continuous "slopping over of the oil and liquid refrigerant into the top of pipe 48. At the left. outlet 48 is connected by a pipe 16 with heat-exchange Pipe I0 1 shown also in Figure 1).

As pointed out above, heat-exchange pipe I0 is immersed in the water in tank 2 to help precool the water; this precooling of the water evaporates any liquid refrigerant present and superheats the gas refrigerant so that the gas refrigerant passing from heat-exchange pipe to is superheated an amount depending upon'the setting of the thermal valve 14 and the temperature of the water in the tank. From heat-exchange pipe ID, the gas refrigerant and oil are carried by a pipe 92 passed'through a thermometer well 94, a T- coupling 98 carrying a gauge 98, to a compressorcondenser unit (not shown).

- The thermal well 94 contains a thermometer bulb connected by tube I02 with the control valve 14 by which the amount of refrigerant entering the line 46 is controlled to maintain-the temperature of the refrigerant gas leaving through the line 92 at substantially a-predetermined temperature. The pressure in line 92 under usual operating conditions remains substantially constant, it being the pressure on the suction side of the compressor for the refrigerating system. Therefore, in order for the valve I4 (acting in response to the temperature in line 92) to control refrigerant flow to maintain a predetermined temperature in the line 92, the vapor in the line 92 must be superheated (the superheating being supplied by the water in which the coils l9 are immersed), for otherwise the temperature in the line 92 would necessarily "be the equilibrium temperature of the refrigerant corresponding to the pressure in line 92. So under usual operating conditions, because the temperature of the water surrounding the coils l remains substantially constant, the control valve 14 and its associated thermometer well 96 serves to maintain the gas in line 92 superheated at substantially a predeter mined number of degrees above the saturation temperature of the refrigerant.

In practice, the control valve 16 is adjusted so that a slight amount of liquid refrigerant floods over into the outlet line 49 and into thecoil 60 carrying with it in solution any oil present. The heat absorbed from the water by the coil I0 in the tank 2 vaporizes this small amount of liquid refrigerant and also heats the gas so that it is superheated. The construction and proportioning of coil I9 is such that the gas velocity is sufiiciently high to sweep with it oil residue left by the vaporized refrigerant and so carries the oil back to the compressor crank case. In addition, the coil 89 serves to precool the water in the tank 2. Full advantage is taken of the cooling of the feed water in connection with the use of the feed water to regulate the tempering of the ice.

As has been indicated above, it is important that the sheet of ice be in proper condition at the time it reaches the wedge unit 9. It has been found that desirable results in this respect can be obtained by supplying the feed'water to tank 2 through the spray pipe 8 in the manner shown best in Figure 1, the control being by means of a float 9 which controls a valve (not shown). The water continually flows onto the sheet of ice after the ice moves above the top of the refrigerant within the cylinder and before the ice reaches the wedge unit 6.

The position of spray pipe 8 is so adjusted with respect to the wedge unit that sufllcient time elapses after the spraying occurs for the ice to reach the proper temperature. The thickness of the sheet of ice depends in part upon the rate of rotation of the cylinder 4; under some conditions, this rate of rotat o is varied from onehalf to one revolution per minute with corre-' sponding variations in ice thickness from about seven one-hundredths of an inch to one-quarter of an inch or more.. The thickness of the ice also depends upon the temperature within the evaporator, which has been varied under some circumstances from 0 F. to 20 F. As indicated above, the capacity of the machine does not vary greatly with changes in the initial temperature of the make-up water, even though this tempera.- ture varies between 40 F. and F.

In the present embodiment, the strips of ice removed from the cylinder are approximately two inches wide. Cylinder 4 is sixteen and threeeighths inches in diameter and has a freezing surface which is eleven and one-half inches wide. Wedge unit 8 is three and nine-sixteenths inches in diameter and is twelve and seven-eighths inches long. The water level in tank 2 is maintained at a point substantially one and one-half inches below the top of the cylinder.

As many possible embodiments may be made of the mechanical features of the above invention and as the art herein described might be varied in various parts, all without departing from the scope of the invention, it is to be understood that all matter hereinbefore set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

I claim:

1. In apparatus for manufacturing a congealed product, in combination: a substantially rigid freezing surface; means for supplying liquid to be congealed to said surface to form a sheet of congealed material thereon; and means for removing successive body portions of said sheet of congealed material from said surface, comprising, wedging means including a wedging edge and means mounting said wedging means and said surface for relative movement with respect to each other to cause said wedging edge to successively progress across said sheet while having substantially only single point contact with said sheet to wedge successive body portions of said sheet free from said sheet and from said surface.

2. In congealing apparatus, the combination of: means to deposit a liquid upon one surface of a rigid member; means to withdraw heat from the liquid through said rigid member to thereby congeal the liquid; means. to regulate the temperature of the congealed liquid to temper it for a subsequent wedging treatment; and wedge means mounted to rotate and thereby move towards said surface and wedge the tempered congealed liquid free from said rigid surface.

3. In ice-making apparatus, the combination of means to deposit a liquid upon one surface of a rigid member; means to withdraw heat from the liquid through said rigid member to thereby form ice; means to regulate the temperature of the ice by spraying it with the liquid to be congealed to temper the congealed liquid for a subsequent wedging treatment; and wedge means mounted to rotate and thereby move towards said surface and wedge the tempered congealed liquid free from said rigid surface.

4. In apparatus of the class described, the' combination of: a substantially cylindrical rigid surface adapted to congeal thereon material supplied thereto; a wedging unit including a helical wedge extending substantially across said rigid surface; means rotatably mounting said rigid surface and said wedging unit to have parallel spaced axes, said axes being spaced apart a distance which is slightly in excess of the totalof the radius of said rigid surface and the radius of rotation of said wedging unit; and means to rotate said rigid surface so that the congealed material on said rigid surface engages said wedge starting at one end of said wedge and continuing to the other end thereof to thereby impart movement to said wedging unit so that said wedge is moved with a peripheral velocity which is substantially that of the rigid surface, and the wedging action of said wedge serving to progressively free the congealed material from the rigid surface.

5. In apparatus of the class described, the combination of a substantially cylindrical rigid surface adapted to congeal thereon material supplied thereto; a wedging unit including a plurality of helical wedges extending substantially across said rigid surface, said wedges overlapping at their ends in an arcuate direction; means rotatably mounting said rigid surface and said wedging unit to have parallel spaced axes, said axes being spacedapart a ,distance which is slightly in excess of the total of the radius of said rigid surface and the radius of rotation of said wedging unit; and means to rotate said rigid surface so that the congealed material on said rigid surface engages successive ones of said wedges starting at one end of each wedge and continuing to the other end thereof, the engagement of the ice with one wedge continuing until the next succeeding wedge is engaged to thereby impart movement to said wedging unit so that said wedge is moved with a peripheral velocity which is substantially that of the rigid surface, and the wedging action of said wedge serving to progressively free the congealed material from the rigid surface.

6. In ice-making apparatus, the combination of a tank to hold water to be frozen; a cylinder rotatably mounted in said tank and positioned to be partially immersed in the water and with its axis extending horizontally, said cylinder having a polished outer rigid cylindrical freezing surface formed of steel containing approximately eighteen per cent chromium and eight per cent nickel; means to refrigerate said cylinder from within to form a sheet of ice upon said freezing surface; wedge means to remove the ice from said cylinder where it extends from the water; and means to spray the water to be frozen onto the sheet of ice to temper the ice prior to removal.

7. In ice-making apparatus, the combination of: a tank to hold water to be frozen; a cylinder rotatably mounted in said tank and positioned to be partially immersed in the water and with its axis extending horizontally, said cylinder being substantially sixteen and three-eighths inches in diameter and having an outer rigid freezing surface extending axially substantially eleven and one-half inches; means to refrigerate said cylinder from within to form a sheet-of ice upon said freezing surface; wedge means to remove the ice from said cylinder where it extends from' the water; and means to spray the water to be frozen onto the sheet of ice to temper the ice prior to removal.

8. In ice-making apparatus, the combination of: a tank to hold water to be frozen; a cylinder rotatably mounted in said tank and positioned to be partially immersed in the water and with its axis extending horizontally, said cylinder being substantially sixteen and three-eighths inches in diameter and having an outer rigid freezing surface extending axially substantially eleven and one-half inches; means to refrigerate said cylinder from within to form a sheet of ice upon said freezing surface; wedge means to remove the ice from said cylinder where it extends from the water, said wedge means comprising six evenly spaced wedges mounted to rotate about an axis at a radius of substantially three and nine-sixteenths inches; and means to spray the water to be frozen onto the sheet of ice to temper the ice prior to removal. 6

9. In the art of congealing liquids, the steps of: supplying liquid to be congealed to a substantially rigid surface: withdrawing heat from said surface to thereby form a layer of congealed liquid thereon; tempering the congealed liquid; and wedging successive portions from a free edge portion of the layer of tempered congealed liquid while congealed to said surface to thereby free such successive portions from the layer and surface.

10. In the art of congealing liquids, the steps of: supplying liquid to be congealed to a substantially rigid surface; withdrawing heat from said surface to thereby form a layer of congealed liquid thereon; regulating the temperature of the congealed liquid; and wedging successive portions of the layer of congealed liquid while congealed to said surface to thereby free said portions from said surface and said layer.

11. In the art of congealing liquids, the steps of: supplying liquid to be congealed to a substantially rigid surface; withdrawing heat from said surface to thereby form a layer of congealed liquid thereon; regulating the temperature of the congealed liquid by spraying it with the liquid to be congealed; and wedging successive portions of said layer of congealed liquid while congealed to said surface to thereby free said portions from said layer and said surface.

12. A process for manufacturing ice fragments comprising: congealing a sheet of ice on a substantially rigid freezing surface; regulating the temperature of the ice to control its hardness and brittleness such that upon subsequent wedging force applied in a direction normal to the freezing surface successive portions of the ice may be substantially completely separated from the surface in pieces as thin as seven hundredths of an inch; and subsequently so wedging successiv e portions of ice from said .ice sheet and from said freezing surface.

13. A process for manufacturing ice fragments comprising: congealing a sheet of ice on a substantially rigid freezing surface; regulating the temperature of the ice by spraying water thereon to control its hardness and brittleness such that upon subsequent wedging action successive portions of the ice may be substantially completely separated from the surface in pieces as thin as about seven hundredths of an inch; and subsequently so wedging successive portions of ice from said ice sheet.

14. A process for manufacturing ice fragments comprising: congealing a sheet of ice on a substantially rigid freezing surface; regulating the temperature of the ice to control its hardness and brittleness such that upon subsequent wedging action successive portions of the ice may be substantially completely separated from the surface in pieces as thin as about seven hundredths of an inch; and subsequently progressively removing sections from said ice sheet by progressively moving a wedging force along an edge portion of said sheet, which wedging force is effective only at a single point at any one instant.

15. In apparatus for manufacturing a brittle product. in combination, means to congeal a fluid in sheet form upon a movable rigid surface, and a wedge having a cuttingredge mounted to move into contact with said sheet while travelling in the direction of travel of said sheet to wedge strips of the sheet free from the rigid surface.

16. In apparatus of the class described, the

combination of means to cohg'eai a fluid in sheet form upon a rigid congealing surface, mounting means, wedge means having a helically-shaped cutting edge rotatably mounted upon said mounting means, and means for relatively moving said surface and wedgemeans to cause said cutting edge to have a cycloidal motion with respect to said congealing surface to cause said cutting edge successively and progressively to contact said sheet to wedge edge portions thereof free from said sheet and from said congealing surface.

17. In congealing apparatus the combination of means to deposit a liquid upon one surface of a rigid cylindrical member, means to withdraw heat from the liquid through said rigid member to congeal the liquid thereon in sheet form, rotatable wedging means, and means for relatively moving said wedging means and said cylindrical member to cause said wedging means to have epicycloidal movement with respect to said surface to successively and progressively wedge edge portions of the sheet free from the surface.

18. In apparatus of the class described, the combination of a rotatable cylinder having a rigid freezing surface to congeal thereon in the form of a sheet fluid supplied thereto, a wedging unit in-- eluding an elongated helical wedge extending substantially across said rigid surface, means for rotatably mounting said wedging unit with respect to said cylinder so that the axes thereof are parallel and are spaced apart a distance slightly in excess of the sum of the radii of said cylinder and of said wedging unit, and means to rotate said cylinder so that the successive leading edge portions of the sheet congealed thereon progressively engage said helical wedge and drive the same to give it epicycloidal movement with respect to the surface of said cylinder and cause it to successively and progressively wedge the edge portions free from said sheet and from said surface.

19. In congealing apparatus the combination of means to deposit a liquid upon one surface of a rigid member, means to withdraw heat from the liquid through said rigid member thereby to congeal the liquid in a layer on said surface, means to regulate the temperature of said congealed layer to temper it for a subsequent treatment, and means for removing successive edge portions of said congealed layer including means for applying to thebody of each edge portion force in a direction along the surface and away from the main body of said congealed layer to break the bond between said edge portion and said surface to free the edge portion as a body from said surface without overcoming the compressive strength of said edge portion.

20. In the art of congealing liquids the steps of supplying liquid to be congealed to a substantially rigid surface, withdrawing heat from said surface thereby to form a layer of congealed liquid thereon, tempering the layer of congealed liquid, and applying force to an edge portion of the congealed layer in a direction along the surface, said force acting through the body of said edge portion to break the bond between said edge portion and the surface to free said edge portion as a body from said surface without overcoming the compressive strength of said tempered portion.

21. A process for'manufacturing ice fragments comprising congealing a sheet of ice on a substantially rigid freezing surface, regulating the temperature of the ice to control its compressive strength to be such that it can withstand the compressive force applied through an edge portion of the ice along the surface to break the bond between such edge portion and the surface, and subsequently applying such forces successively to remove successive edge portions of ice from said ice sheet.

22. In congealing apparatus the combination of means to supply a fluid to one surface of a rigid member, means to withdraw heat from the fluid through said rigid member thereby to congeal the fluid in a brittle layer on said surface, and means for substantially continuously applying a force to said layer successively progressing along narrow areas extending diagonally across said layer and spaced rearwardly from the leading edge of said layer to remove bodily successive edge portions of said layer from said surface and layer, said force acting in a direction along the surface through the body of each such successive edge portion to break the bond between each such edge portion and the surface without overcoming the compressive strength of the body of the edge portion against which the force is applied.

23. In congealing apparatus the combination of means to supply a fluid to one surface of a rigid member, means to withdraw heat from the fluid through said rigid member thereby to congeal'the fluid in a brittle layer on said surface, and means for substantially continuously applying a force to said layer successively progressing along narrow areas extending diagonally across said layer and spaced rearwardly from the leading edge of said layer to remove bodily successive fectively staggered about the axis of rotation of said rotating means to cut into said layer progressively along said diagonal narrow areas to apply said force in the manner described.

24. In congealing apparatus the combination of means to supply a fluid to one surface of a rotating cylindrical rigid member, means to withdraw heat from the fluid through said member thereby to congeal the fluid in a brittle layer on said surface, means for substantially continuously applying a force to said layer successively progressing along narrow areas extending diagonally across said layer and spaced rearwardly from a leading edge of said layer to remove bodily successive edge portions of said layer from said surface and layer, said force acting in a direction along the surface through the body of each such successive edge portion to break the bond between each such edge portion and the surface without overcoming the compressive strength of the body of the edge portion against which the force is applied, said means including rotating blade-carrying means extending across said surface and having force-applying edges effectively staggered about the axis of rotation of said rotating means, and means forrotating said member and means for driving said rotating means to cause said edges to apply said force to said edge portions in the manner described.

25. The method of manufacturing a brittle product comprising supplying fluid to one surface of a rigid member, withdrawing heat from the fluid through said rigid member to congeal the fluid in a brittle layer on said surface, substantially continuously applying a force to said layer successively progressing along narrow areas extending diagonally across said layer and fspaoed rearwardly from the leading edge of said layer to remove bodily successive edge portions of said layer from said surface and layer and applying I said force "in a direction along the surface applied.

FRANCIS M. RAVER. 

